Sputtering, alternatively called physical vapor deposition (PVD), has long been used in depositing metals and related materials in the fabrication of semiconductor integrated circuits. Its use has been extended to depositing metal layers onto the sidewalls of high aspect-ratio holes such as vias or other vertical interconnect structures. Currently, advanced sputtering applications include depositing a metallic seed layer for later electroplating of the metallic layer in the via and depositing a barrier layer on the dielectric material of the via sidewall to prevent the metallic layer from diffusing into the dielectric.
Plasma sputtering may be accomplished using either DC sputtering or RF sputtering. Plasma sputtering typically includes a magnetron positioned at the back of the sputtering target to project a magnetic field into the processing space to increase the density of the plasma and enhance the sputtering rate. The inventors have observed that as the distance between the substrate and the sputtering target is increased, the plasma density and volume can be increased to advantageously improve overall bottom coverage on the substrate. However, because of the ion density and diffusion of the ions in the plasma, as the distance between the substrate and the sputtering target is increased, the more difficult it becomes to meet the uniformity and particle performance since the magnetron influence decreases.
Thus, the inventors have provided a magnet configuration that can advantageously be used to deposit materials while improving particle performance.